UMMS Affiliation

Department of Biochemistry and Molecular Biology

Date

3-14-1998

Document Type

Article

Subjects

Animals; Binding, Competitive; Biological Transport; Dogs; Endoplasmic Reticulum, Rough; Molecular Chaperones; Pancreas; Protein Processing, Post-Translational; Protein Sorting Signals; Proteins; Rabbits; Ribosomes; Seeds; Signal Recognition Particle; *Trans-Activators; Triticum

Disciplines

Life Sciences | Medicine and Health Sciences

Abstract

Proteins with RER-specific signal sequences are cotranslationally translocated across the rough endoplasmic reticulum through a proteinaceous channel composed of oligomers of the Sec61 complex. The Sec61 complex also binds ribosomes with high affinity. The dual function of the Sec61 complex necessitates a mechanism to prevent signal sequence-independent binding of ribosomes to the translocation channel. We have examined the hypothesis that the signal recognition particle (SRP) and the nascent polypeptide-associated complex (NAC), respectively, act as positive and negative regulatory factors to mediate the signal sequence-specific attachment of the ribosome-nascent chain complex (RNC) to the translocation channel. Here, SRP-independent translocation of a nascent secretory polypeptide was shown to occur in the presence of endogenous wheat germ or rabbit reticulocyte NAC. Furthermore, SRP markedly enhanced RNC binding to the translocation channel irrespective of the presence of NAC. Binding of RNCs, but not SRP-RNCs, to the Sec61 complex is competitively inhibited by 80S ribosomes. Thus, the SRP-dependent targeting pathway provides a mechanism for delivery of RNCs to the translocation channel that is not inhibited by the nonselective interaction between the ribosome and the Sec61 complex.

Rights and Permissions

Citation: Mol Biol Cell. 1998 Jan;9(1):117-30.

Related Resources

Link to Article in PubMed

Journal Title

Molecular biology of the cell

PubMed ID

9436995

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